The invention relates to an electrical power supply of an X-ray tube comprising: a high voltage generation device configured to transmit a high voltage to the X-ray tube comprising: a primary capacitor; at least one voltage source configured to supply the primary capacitor; an energy storage device comprising: an auxiliary capacitor configured to receive from the primary capacitor a quantity of energy and to return said energy to the primary capacity; a control device arranged between the generation device and the storage device, the generation, storage and control devices being connected in series, the control device being capable of connecting or isolating the storage device from the generation device such that the X-ray tube is powered by a variable high voltage very rapidly between a first high voltage and a second high voltage.